On 05/13/2010 03:12 PM, Peter Zutrauen wrote:
> The confusion around this topic (thus your "failure" ;-) may be (/at
> least it was in my case/ :-P ) that one has to accept the fact that the
> design's torque tube placement results in a (symmetrical airfoil)
> tailplane is *aerodynamically balanced* for Frans' functional
> description to make sense. ie- no matter what the steady-state angle of
> incidence is of the tailplane, there are no resultant stick forces which
> need to be zero'd out by a portruding trim-tab ( which is the anti-servo
> tab in this case).
Ah, OK, now I see your point.
I thought that this aerodynamically balance was the major "selling
point" of the tailplane, and hence common knownledge amongst builders. I
recall having read somewhere that the whole purpose of the mass balance
arm is to cancel out the weight offset, which is a *result* of having
the torque tube in the aerodynamic center, rather than in the weight center.
I have to admit that it took me a while too before I grabbed the
concept. The whole arrangement with the anti servo tabs which double
duty as trim tabs at the same time is indeed a genious concept. If the
anti servo tabs are always in line with the tailplane, there is never a
drag penalty, regardless of trim setting. This is just one of the things
that make the Europa a relatively fast airplane.
Then you can maybe understand that I found it rather shocking to read
that "all Europa's are flying with the trim tabs deflecting upwards"...
as this would defeat the whole purpose of the ingenious anti servo tab
and all flying tailplane. I was prepared to find a way to fix this
problem once I would reach the flying stage... until I discovered to my
delight that the PH-DIY doesn't suffer from this problem at all.
I'm still curious however why some Europa's suffer this problem.
> I'm still curious how close to perfectly aerodynamically balanced the
> tailplane design is. Don Dykins sure was a clever fellow.
Was Don Dykins responsible for the tailplane too? He was indeed a clever
fellow.
Frans
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